Among adolescents living in culturally diverse social contexts, acculturation to the United States culture has been identified as a risk factor for substance use. However, the complexities of acculturation processes and their influences on health risk behaviors remain only partially understood. Multiple patterns of adolescent acculturation are possible, including Assimilation, Separation, Marginalization, and several bicultural patterns of behavior such as Alternation, Fusion, and Integration. Previous studies of adolescent acculturation and its consequences have not considered the family and peer contexts in which acculturation and ethnic identity formation occur. Understanding the social contexts of acculturation is important because most psychosocial risk factors for adolescent substance use involve peer and family influences. In immigrant families, multiple generations of family members are acculturating, typically at differing rates and with different patterns. Parent child discrepancies in acculturation patterns might affect parental authority and parent-child communication, which in turn might influence the adolescents' selection of peers and activities and ultimately the adolescents' involvement in substance use. This study will examine adolescent acculturation patterns in the family context, the effects of parent-child acculturation patterns on family functioning, the effects of family functioning on peer social networks, and the effects of social networks on adolescent substance use. The study will consist of a year of qualitative and pilot research, followed by a three-year longitudinal study. Over a three-year period, high school students in ethnically diverse and non-diverse high schools in Southern California (N=2000) and their parents will complete questionnaires about their acculturation patterns and family functioning. Social network analysis will be used to describe the structure of the adolescents' social networks and the prevalence of substance use among social network members. The individual-level data from students and parents will be matched with U.S. Census data to obtain information about the ethnic composition of the neighborhood. Analyses will be conducted to understand the psychosocial mechanisms by which multigenerational acculturation patterns influence the risk of adolescent substance use, and the role of the social network and ethnic context on those processes. The results will provide important information that can be used to develop more effective substance use prevention programs for ethnically diverse adolescents in acculturating families in a multicultural society. [unreadable] [unreadable]